ES2625089T3 - Surgical drill with odd grooves - Google Patents

Abstract

A surgical dissection tool for cutting bone and other tissues, comprising: a distal end portion (104); a proximal end portion (102); a rod (106, 206, 306) extending between the distal end portion (104) and the proximal end portion (102); a cutting head (120, 220, 320) at the distal end portion (104) connected to the rod (106, 206, 306), the cutting head (120, 220, 320) having an outer surface (122, 222 , 322), the outer surface (122, 222, 322) having an odd number of grooves (124, 224, 324) formed therein, each slot comprising: - a tilting surface (126, 226, 326) that is crosses with the outer surface (122, 222, 322) to form a cutting edge (128, 228, 328), - a bead surface (130, 230, 330) opposite the tilt surface (126, 226, 326), the bead surface (130, 230, 330) and the tilt surface (126, 226, 326) forming a first angle, and - a front angle surface (132, 232, 332) extending from the bead surface (130, 230, 330) to a distal end portion of the cutting head (120, 220, 320); characterized in that the front angle surface and the tilt surface (126, 226, 326) form a second angle substantially the same as the first angle.

Description

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DESCRIPTION

Surgical strawberry with odd grooves Field of the invention

The present description is directed to a surgical system to cut bones, or to shape them, and, more particularly, to a surgical dissection tool of the surgical system.

Background

During surgical interventions in which cutting tools are used, surgeons often weigh the aggressiveness of the cutting tools and the ability to precisely control the cutting tool. When a surgeon controls the cutting instruments to increase aggressiveness, potentially reducing the duration of the surgical intervention, the surgeon may have less precise control. Although the non-aggressive cut may be more precise, it can increase the duration of the surgical intervention.

A part of the lower precision during aggressive cutting may be due to the vibration of the tool. The tool may vibrate for different reasons. One reason is the separation of the slots. A cutting tool with “in pairs” grooves or an even number of grooves can vibrate because one edge is woven together with another edge disengaged from the fabric or it can occur when the depth of cut of several gear grooves varies, which produces asymmetric forces. In addition, the vibration of the tool may be due to the fact that the fabric cannot exit the grooves before the groove re-engages tissue. This can be aggravated during an aggressive cut that can result in relatively large pieces of tissue.

An example of a cutting tool is described in US 5810517 A, in which a rotary cutting tool includes three edges of complex configuration, equidistant and lowered.

The present description is directed to a surgical system for cutting bones, or shaping them, that solves one or more of the limitations of the prior art.

Summary of the invention

In an exemplary aspect, the present description is directed to a surgical dissection tool for cutting bone and other tissues. The dissection tool may include a distal end part and a proximal end part. A rod can extend between the distal end part and the proximal end part. A cutting head, placed at the distal end part, is connected to the stem. This has an outer surface that has an odd number of grooves formed therein. Each groove includes an inclination surface that intersects the outer surface to form a cutting edge and an offset surface opposite the inclination surface. The bead surface and the tilt surface form a first angle. Each slot also includes a front angle surface that extends from the bead surface to a distal end portion of the cutting head, the front angle surface and the tilt surface forming a second angle substantially equal to the first angle.

In one aspect, the odd number of slots comprises three slots. In another aspect, the first and second angles are obtuse angles. In another aspect, the front angle surface comprises one of a chamfer and a round. In another aspect, the groove also comprises a bevel between the front angle surface and the tilting surface.

In another exemplary aspect, the present description is directed to a surgical dissection tool, for cutting bone and other tissues, which includes a rod and a cutting head connected to the rod. The cutting head and the rod have a central longitudinal axis and the cutting head has an outer surface that has an odd number of grooves formed therein. Each groove can include a flat tilt surface that intersects the outer surface to form a cutting edge and can include a flat bead surface opposite the tilt surface. The flat tilt surface and the flat bead surface form an obtuse angle. A front angle surface can extend from the flat bead surface to a distal end portion of the outer surface and the front angle surface of at least one of the grooves includes a more distal end that protrudes from the longitudinal axis.

In another exemplary aspect, the present description is directed to a surgical dissection tool, for cutting bone or other tissues, which includes a rod and a cutting head connected to the rod. The cutting head and the rod can have a central longitudinal axis and an outer surface. The outer surface can be substantially spherical in shape and can have three grooves formed therein. The outer surface between adjacent grooves of the three grooves forms an angle between approximately 45 and 55 degrees. Each slot in the three slots includes a flat tilt surface that intersects the outer surface to form a cutting edge. The flat inclination surface is parallel to a reference plane through the longitudinal axis and this

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off-center with respect to it. Each slot also includes a flat bead surface opposite the tilt surface and intersects with the outer surface. The flat bead surface can extend to a proximal part of the cutting head, the flat tilt surface and the flat bead surface can form a first obtuse angle between about 95 and 105 degrees. A front angle surface can extend from the flat bead surface to a distal end portion of the outer surface. The front angle surface and the flat bead surface can form a second angle substantially the same as the first obtuse angle. The front angle surface of at least one of the three grooves may include a more distal end that protrudes from the longitudinal axis.

In another exemplary aspect, the present description is directed to a surgical system that has a trepan assembly of surgical dissection with a surgical dissection tool as described herein.

Brief description of the drawings

A more complete understanding of the present disclosure and advantages thereof can be achieved by referring to the following description taken in conjunction with the accompanying figures.

Figure 1 is an illustration of a trepan assembly of surgical dissection according to the use of the present invention in a patient.

Fig. 2 is a illustration of a partially exploded perspective view of a trepan assembly of surgical dissection including a drive device and a surgical dissection tool according to the present invention.

Figure 3 is an illustration of an isometric view of a distal end of a surgical dissection tool according to an example aspect of the present description.

Figure 4 is an illustration of a side view of a surgical dissection tool according to an example aspect of the present description.

Figure 5 is an illustration of a view from one end of a distal end of a surgical dissection tool according to an example aspect of the present description.

Figure 6 is an illustration of a side view of a distal end of a surgical dissection tool according to an example aspect of the present description.

Figure 7 is an illustration of another side view of a distal end of a surgical dissection tool of Figure 6, rotated from the position of Figure 6 according to an example aspect of the present description.

Figure 8 is an illustration of a view from one end of a distal end of a surgical dissection tool according to an example aspect of the present description.

Figure 9 is an illustration of an isometric view of a distal end of a surgical dissection tool according to another example aspect of the present description.

Figure 10 is an illustration of a side view of a surgical dissection tool according to an example aspect of the present description.

Figure 11 is an illustration of another side view of a surgical dissection tool according to an exemplary aspect of the present description, rotated from the side view shown in Figure 10.

Figure 12 is an illustration of a view from one end of a distal end of a surgical dissection tool according to an example aspect of the present description.

Figure 13 is an illustration of a view from one end of a distal end of a surgical dissection tool, in terms of bone tissue, cutting a path in the tissue according to an example aspect of the present description.

Detailed description

Now, reference is made in detail to exemplary embodiments of the invention, the examples of which are illustrated in the accompanying drawings. To the extent possible, the same reference numbers are used in all drawings to refer to the same or similar parts.

The present description is directed to a trepan assembly of surgical dissection that includes a dissection tool drive device that drives a surgical dissection tool during

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surgical interventions. The dissection tool can provide greater cutting control and cutting precision by reducing the incidence of vibration during cutting. This can allow a surgeon to make more aggressive dissections without compromising the control and precision of the cut. In turn, this can reduce the time needed for some surgical interventions, which benefits the patient. In addition, less vibration can result in more uniform cuts, which can improve healing and reduce recovery times.

The sample dissection tool, which is described in this document, is a surgical burr that has odd grooves. As such, the slots themselves are not exactly 180 degrees apart. Off-center grooves seem to be advantageous for less vibration, while allowing relatively aggressive cutting. The advantage may be due to time differences, since during a single rotation of the dissecting cutter a groove gears to cut tissue while another disengages from the tissue.

Figure 1 shows a patient A who is undergoing neurosurgery. In accordance with normal practice, access to the brain or other neural structures often requires a delicate dissection of bone and other tissues in order to access. By way of example, a dissecting trepan assembly is shown that makes use of a dissection tool drive device 10 according to an aspect of the present invention, which is being used to dissect a bone part of a patient A and other tissues adjacent to the surgical access point.

Figure 2 illustrates the dissection tool drive device 10, for dissecting bone or other tissues, in more detail. The dissection tool drive device 10 includes a motor housing 12, coupled to a hose and air duct assembly 14 that supplies pressurized air to a motor of the motor housing 12 and draws the outlet air at low pressure of the surgical point. The dissection tool drive device 10 further includes a coupling housing 16 that is connected to a dissection tool 100. The dissection tool 100 is described in more detail with reference to Figures 3 to 5.

Figure 3 shows an isometric view of a distal end part, Figure 4 shows a side view of the dissection tool 100 and Figure 5 shows a view from one end of the distal end part. Referring to these figures, the dissection tool 100 is, in this example, a surgical burr that includes a proximal end portion 102 and a distal end portion 104 connected by an extendable shaft or shaft 106. The rod 106 has an axis longitudinal 108 defining a central line of the proximal end portion 102 and the distal end portion 104. In one embodiment, the rod 106 includes a diameter between about 0.0762 and 0.381 cm (0.030 and 0150 inches).

The proximal end portion 102 is arranged to engage with a shaft of the motor part 12, and be driven by it, but it crosses the coupling housing 16 of Figure 2 and is held therein. In this example, the proximal end portion 102 includes a first non-circular zone 112 when viewed in cross-section, a second non-circular zone 114 when viewed in cross-section and an intermediate zone 116. In this example, the first and the Second non-circular zone 112, 114 are shown as hexagonal shaped surfaces and have the same transverse shape. These zones are configured to engage with a drive part of the dissecting tool drive device 10. The intermediate zone 116 has a cross-sectional area smaller than the first and the second non-circular zone 112, 114. It can be used to engage with the dissection tool drive device 10, or to be engaged by it, to anchor or otherwise secure the dissection tool 100 in the dissection tool drive device 10. In this example, the intermediate zone 116 has a section cross section with a diameter smaller than the minimum width of the cross section of the first non-circular zone 112.

The distal end portion 104 includes a cutting head 120 connected to the rod 106. The cross section of the cutting head 120 is larger than the diameter of the rod 106. The cutting head 120 is shown as a surgical cutter with a surface outer 122. In this example, outer surface 122 is substantially spherical. In other embodiments, the cutting head 120 may have a cross section smaller than at least a portion of the rod 106. In one embodiment, the rod 106 includes a neck with a curved or conical surface that extends to the cutting head 120.

The cutting head 120 is formed with three symmetrical cutting grooves 124 formed on the outer surface 122 and uniformly spaced around the cutting head 120. Each cutting groove 124 includes an inclination surface 126 that forms a cutting edge 128 with the outer surface 122 and includes a bead surface 130 adjacent to the inclination surface 126. A distal area of the cutting head 120 includes a front angle surface shown as a chamfer part 132 oriented toward the bead surface 130. A bevel 134 connects the chamfer part 132 to the tilting surface 126. As can be seen, the edge 120 forms a uniform arc from the most distal part of the spherical cutting head 120 to the proximal side of the cutting head 120.

In this example, the inclination surface 126 is a flat surface along its entire length. In this case, the inclination surface 126 is offset from a plane that crosses the longitudinal axis 108, but is

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parallel to it. Therefore, the inclination surface 126 is in a plane that does not cross the central line or longitudinal axis 108 of the dissection tool 100. Although it is shown off-center behind the central line, in other embodiments, the inclination surface 126 is offset from to a plane before or in front of a plane that crosses the longitudinal axis, but is parallel to it, to impart a desired angle of inclination. In one embodiment, the inclination surface is positioned such that a plane through the angle of inclination crosses the axis corresponding to a neutral angle of inclination. Although flat, in other embodiments, the inclination surface 126 is angled or is formed by a propeller.

The bead surface 130 forms the opposite side of the groove 124 and, together with the inclination surface 126, forms an angle 0 of between approximately 85 and 120 degrees, although other angles are contemplated. In one embodiment, the angle 0 is between about 95 and 105 degrees and, in another embodiment, the angle is about 100 degrees. The bead surface extends from the chamfer part 132 to a proximal part of the cutting head 120. Different embodiments of the dissection tool 100 include angles between the inclination surface 126 and the bead surface 130 which are sharp, straight or obtuse In some embodiments, angle 0 is between about 90 ° and 100 °.

As best seen in Figure 4, the chamfer part 132 tilts from the bead surface 130 to a distal end of the cutting head 120. In the example shown, the chamfer part 132 is cut at an angle to measured from a transverse line to axis 108 so that it decreases between approximately 20 and 70 degrees. In one example, the chamfer part 132 is formed with an angle a between about 35 and 45 degrees and, in one example, the angle a is about 40 degrees. The angle a is formed so that the end of the chamfer part 132 protrudes from the center line or axis 108, as can be seen in Figure 4. Also, in the embodiment shown, the chamfer part 132 is formed , with respect to the inclination surface 126, to form an angle that substantially corresponds to the angle 0 formed between the embossment surface 130 and the inclination surface 126.

Figure 5 shows how the bevel 134 intersects the outer surface 122 of the cutting head 120 to form a front surface with the outer surface 122 at the most distal end of the cutting head. The bevel 134 tilts from the edge 128 so that each slot 124 is independent of the rest of the grooves and does not cross them, although each protrudes from the center line or axis 108. In the embodiment shown, the cutting head 120 , although spherically, it includes a truncated proximal end that is welded with brass to rod 106.

Figures 6 to 8 show a further embodiment of a dissection tool, in this case referenced with the number 200. Some of the sizes, angles and characteristic shapes of the dissection tool 200 are similar to those described above, and they will not repeat themselves. The dissection tool 200 includes a rod 206 and a proximal end similar to the rod and the proximal end that have been previously analyzed with reference to the dissection tool 100. Therefore, in this case they will not be described in detail.

The dissection tool 200 includes a cutting head 220 with a spherical outer surface 222 having three cutting slots 224a to 224c formed therein, each cutting slot 224a to 224c having a respective flat tilt surface 226a to 226c that crosses the outer surface 222 to form a respective edge 228a to 228c. A bead surface 230a to 230c forms a wall opposite to each respective inclination surface 226a to 226c of each cutting groove 224a to 224c. As described above, in one embodiment, the inclination surfaces 226 are parallel to a plane through the center line or axis 208, but are offset from it. In other embodiments, the inclination surfaces 226 form planes that cross the center line or axis 208.

Instead of having identical grooves, as described with reference to the dissection tool 100, the dissection tool 200 includes cutting slots that vary from one to another. In this example, each cutting groove 224a to 224c includes a respective front angle surface that is shown as a chamfer or a round of 232a to 232c that extends from its most distal end to the bead surface 230. However, the chamfers or round 232a to 232c of each slot 224a to 224c have different depths or curvatures. This can be understood by referring to Figure 6 in which each chamfer or round has a different size.

Figures 7 and 8 show an illustration of a side view of the cutting head 220 showing the curvature along the different slots of the dissection tool 200. Figure 7 shows the profile of the bead surface 230c and the chamfer. or round 232c. Figure 8 shows the profile of the bead surface 230a and the chamfer or round 232a. As can be seen, by comparison, the chamfer or round 232a of Figure 8 is substantially larger than the chamfer or round of 232c of Figure 7. As can be seen in Figure 8, the front angle surface comprises both a chamfer. Like a circle. The round connects the chamfer and the bead surface 230a. In addition, the tilting surface 228 continues the entire length of the bead surface 230 and the chamfer or circle 232. That is, the dissection tool 200 does not include a bevel surface. However, since the chamfer or round 232 varies by groove in the example tool 200, the area of the inclination surface also varies from groove to groove. As can be seen by comparing Figures 7 and 8, the area of the inclination surface 226a is greater than the area of the surface of

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226c inclination. Also, the length of the cutting edge varies from groove to groove and cutting edge 228a is greater than that of cutting edge 228c. Also, as shown in Figure 8, the chamfer or round 232a of the cutting groove 224a protrudes from the center line or axis 208 while the cutting grooves 224b and 224c do not protrude from the center line or axis 208.

Figures 9 to 12 show a further embodiment of a dissection tool, in this case referenced with the number 300. Some of the sizes, angles and characteristic shapes of the dissection tool 300 are similar to those described above, and they will not repeat themselves. The dissection tool 300 includes a rod 306 and a proximal end similar to the stems and proximal ends discussed above.

The dissection tool 300 includes a cutting head 320 with an outer surface 322 having three cutting grooves 324 formed therein, each cutting groove 324 having a respective tilting surface 326 that crosses the outer surface 322 to form a cutting edge. 328. In this case, the cutting grooves 324 have a substantially identical shape and, therefore, all are referenced with the same reference number.

In this embodiment, the inclination surface 326 is shaped like a propeller, with a front part 340 and a rear part 342. The propeller angle increases the effective shear action thereby reducing the shear forces and the amount of heat generated during The bone cutting process. You can also improve the expulsion of chips. During cutting, as the mill rotates around the longitudinal axis 308, the front part 340 is the first part that meshes the bone tissue during a cutting action and the rear part 342 follows the front part 340. During cutting, This can provide additional stability to the three-slot milling cutter since the resistance of the bone tissue is applied through a progressive lateral action. This makes the cutting forces more constant, with less possibility of vibration. Instead of the entire edge of a groove engaging the bone at the same time, the propeller causes the front part 340 to engage the bone first and the rest of the cutting edge to engage the bone in a very short time. This reduces both vibration and damping, which results in higher levels of stability.

In this embodiment, the front parts 340 of the respective inclination surfaces 326 are parallel to a front part of a plane through the center line or axis 308, but are offset from it. In other embodiments, the front parts 340 of the tilting surfaces 326 form planes that cross the center line or axis 308 or that are behind a plane through a center line or axis 308. As can be seen in Figure 12, the leading edge extends in front of the center point and protrudes therefrom.

Figure 12 shows a view from one end of the dissection tool 300 with a reference limit 346 that creates a circle that crosses the edges 328 of the dissection tool 300. Although it is shown in cross section as a line, in a For example, the reference limit 346 is a spherical limit that crosses the edges 328. The edges 328 of the dissection tool 300 intersect with the spherical reference limit 346. However, in cross section, the outer surface 322 gradually narrows inwards from the reference limit 346. As can be seen in Figure 12, the outer surface 322 includes a conical part 348 followed by a curved part 350. The conical part 348 extends from the edge, backwards, along of the outer surface 322. The conical part 348 is followed by a curved part 350 that is formed with a variable radius, such as an Archimedes spiral or a cam surface. The cam bead formed due to the conical part and the curved part 350 is marked with the reference number 351. This provides the maximum clearance that allows the cutter to advance towards the bone tissue without excessive interference from the outer surface 322 by engaging the surface. recently cut. This can help reduce the heat that could be produced if the outer surface is engaged with bone tissue or friction.

A bead surface 330 forms a wall opposite each respective inclination surface 326 of each cutting groove 324. In the embodiment of the dissection tool 300, all grooves 324 are substantially identical and are similar to the inclination surfaces that are have described above. A reference line 352 identifies a core thickness of the cutting head 320. The core thickness is the minimum diameter of the solid part of the cutting head. When three grooves are used, as shown in Figure 12, the thickness of the soul has a radius equal to about half the radius of the edges 328. Other embodiments have a thickness of the soul that is greater or less. In one embodiment, the radius of the soul thickness is between about 40% and 80% of the radius of the edges 328.

Figures 10 and 11 show an illustration of a side view of the cutting head 320 showing the curvature along the different grooves of the dissection tool 300. Figure 10 shows the profile of the bead surface 330c and the chamfer. or round 332c. Figure 11 shows the profile of the inclination surface 326 and the edge 328. As can be seen by comparison, the inclination surface 328 forms a propeller that extends from the front part 340 to the rear part 342.

Figure 13 shows the example surgical dissection tool 300 in a cutting environment. In this view, a bottom view of the cutting tool 300 cuts a path in the bone tissue structure 370, the bone tissue structure 370 being transparent in order to visualize the cutting tool.

In Figure 13, the edge 328 of the dissection tool 300 is shown meshed in material of the bone structure 370 and cutting it. Edge 328 is also just engaging in the bone structure 370. As can be seen, at that time, there are only two edges 328 engaged in the bone structure 370. The third edge 328 removed 5 from the gear with the bone structure. Since the grooves are offset and not directly facing each other, the edge 328 is removed from contact with the bone structure before the edge 328 engages the bone structure. The difference in time between the moment in which a woven cutting edge and a different cutting edge is disengaged from the tissue, during a single rotation of the dissecting cutter, can provide advantages in terms of less vibration. Therefore, at each moment, only two of the three edges are in contact with the bone structure.

10

While the example dissection tools are strawberries with three slots, the dissection tools may have additional odd slots. For example, an example of the dissection tool includes five slots. In use, the odd number of grooves can result in a lower level of vibration during bone or cut. Since the cut is produced by rotating the dissection tool around its longitudinal axis, the odd number

15 of grooves compensates the times of the initial gear of the edge and the disengagement of the edge. This time compensation is designed to reduce the incidence of vibration while still allowing an aggressive cutting action. In addition, since at least one of the grooves has an edge that protrudes from the longitudinal axis or central line, the angle at which the surgeon maintains the trepan is not as fundamental as it would have been otherwise.

20 It is evident that the specific illustrative embodiments disclosed above may be altered or modified and all such variations are considered within the scope of the present invention.

Claims (15)

5 10 fifteen twenty 25 30 35 40 Four. Five fifty 55 60 65 1. A surgical dissection tool for cutting bone and other tissues, comprising: a distal end portion (104); a proximal end portion (102); a rod (106, 206, 306) extending between the distal end portion (104) and the proximal end portion (102); a cutting head (120, 220, 320) at the distal end portion (104) connected to the rod (106, 206, 306), the cutting head (120, 220, 320) having an outer surface (122, 222 , 322), the outer surface (122, 222, 322) having an odd number of slots (124, 224, 324) formed therein, each slot comprising: - an inclination surface (126, 226, 326) that intersects the outer surface (122, 222, 322) to form a cutting edge (128, 228, 328), - a bead surface (130, 230, 330) opposite the tilt surface (126, 226, 326), forming the bead surface (130, 230, 330) and the tilt surface (126, 226, 326) a first angle, and - a front angle surface (132, 232, 332) extending from the bead surface (130, 230, 330) to a distal end portion of the cutting head (120, 220, 320); characterized in that the front angle surface and the inclination surface (126, 226, 326) form a second angle substantially the same as the first angle. 2. The surgical dissection tool of claim 1, wherein the odd number of slots (124, 224, 324) consists of three slots. 3. The surgical dissection tool of claim 1, wherein the first and second angles are obtuse angles and wherein the embossment surface (130, 230, 330) extends to a proximal end of the cutting head ( 120, 220, 320). 4. The surgical dissection tool of claim 1, wherein the front angle surface comprises one of a chamfer and a round. 5. The surgical dissection tool of claim 1, wherein the front angle surface comprises both a chamfer and a round. 6. The surgical dissection tool of claim 1, wherein the groove also comprises a bevel between the front angle surface and the tilt surface (126, 226, 326). 7. The surgical dissection tool of claim 6, wherein the groove also comprises a bevel between the front angled surface and the distal end portion of the outer surface (122, 222, 322). 8. The surgical dissection tool of claim 1, wherein each of the slots (124, 224, 324) is substantially identical. 9. The surgical dissection tool of claim 1, wherein a length of the edge of each of the grooves is different between the grooves (124, 224, 324). 10. The surgical dissection tool of claim 1, wherein the outer surface (122, 222, 322) is spherical in shape. 11. The surgical dissection tool of claim 1, further comprising: that the cutting head (120, 220, 320) and the rod (106, 206, 306) have a central longitudinal axis, that the inclination surface (126, 226, 326) is flat, that the bead surface (130, 230, 330) is flat and the tilt surface (126, 226, 326) and the bead surface (130, 230, 330) form an obtuse angle, and that the front angle surface extends from the flat bead surface (130, 230, 330) to the distal end portion of the outer surface (122, 222, 322); 5 10 fifteen twenty 25 30 wherein the front angle surface of at least one of the grooves (124, 224, 324) includes a more distal end protruding from the longitudinal axis. 12. The surgical dissection tool of claim 11, wherein the flat tilt surface is a flat part and the tilt surface comprises a helix. 13. The surgical dissection tool of claim 1, wherein the cutting head (120, 220, 320) and the rod (106, 206, 306) have a central longitudinal axis and an outer surface spherically, having the outer surface only three grooves (124, 224, 324) formed therein, in which the outer surface spherically between adjacent grooves of the three grooves (124, 224, 324) forms an angle between approximately 45 and 55 degrees, each slot comprising the three slots: a flat tilt surface that intersects the outer surface to form the edge (128, 228, 328), the edge (128, 228, 328) of the three grooves being positioned to define a reference limit substantially spherically, in which the flat inclination surface is parallel to a reference plane through the longitudinal axis and is offset from it; a flat bead surface opposite the inclination surface and which intersects the outer surface, the flat bead surface extending to a proximal part of the cutting head (120, 220, 320), forming the flat inclination surface and the flat bead surface a first obtuse angle between approximately 95 and 105 degrees and the front angle surface extending from the flat bead surface to the distal end portion of the outer surface, the front angle surface and the flat bead surface forming the second angle at substantially the same angle as the first obtuse angle, in which the front angle part of at least one of the three grooves (124, 224, 324) includes a more distal end protruding from the longitudinal axis. 14. The surgical dissection tool of claim 13, wherein each of the three slots (124, 224, 324) is substantially identical. 15. The surgical dissection tool of claim 13, wherein the angled surface of each of the three slots (124, 224, 324) varies from one to another.